Ahmia is a good search engine to start with. You'll find more links there. A lot of the stuff you'll find will be scams or mirrors of clearnet sites, and some of it's obvious, like websites selling dumb shit like human meat. IDK about drug recipes if that's what you mean by chemistry and explosive recipes can be found on the clearnet. (Although using TOR is still advised). Stay away from the *****s.
C, but it really depends on what you want to hack.